Abstract:

Geochemical process is one of the most important factors influenced fluid movement, solute transport and heat transfer in porous media such as rock and soil. Based on the unsaturated soil theory established by Fredlund, in which the unsaturated soil porous media has been considered as a media which has four phases, assumed the effect of precipitation/dissolution to be an individual phase. With some hypotheses, the porosity and water content of porous media are modified by solute concentration, a new coupled relation between solute transport and hydraulic parameters has been built. The new relation updates the traditional coupled model in which the impact from solute field acts on seepage flow field by only density and viscosity. Here, a coupled model of multi-phases and multi-components hydraulic-transport-thermal and geochemical processes in variable saturated porous media is established. Using a infiltrate experiment for reactive coal mine gangue in the laboratory, the coupled numerical model is tested. The results show that the water seepage velocity calculated from experiment matches well the outcome from numerical model which considered the precipitation/dissolution coupling variable. Thus the applicability of the numerical model is verified.

Key words: geochemical process, variable saturated media, precipitation/dissolution, coupled model